Which seas belong to the Indian Ocean. The geographical position of the Indian Ocean: description, features. Indian Ocean on the map

The Indian Ocean is the third largest ocean. Geologically, it is mainly a relatively young ocean, although it should be noted, as for other oceans, that many aspects of its earliest geological history and origin have not yet been studied. Western border south of Africa: along the meridian of Cape Agulhas (20° E) to Antarctica (Queen Maud Land). Eastern border south of Australia: along the western border of the Bass Strait from Cape Otway to King Island, then to Cape Grim (North-Western Tasmania) and from the south-eastern tip of Tasmania Island along 147 ° E. to Antarctica (Fischer Bay, George V Coast). With regard to the eastern border north of Australia, there has been much discussion, caused by the fact that some scientists attribute the Arafura Sea, and some even Timor

sea ​​to the Pacific Ocean, although this is not entirely logical, since the Timor Sea is by nature hydrological regime is inextricably linked with the Indian Ocean, and the Sahul Shelf in geological terms is clearly part of the Northwest Australian Shield, connecting the region of the once-existing Gondwana with the Indian Ocean. Most geologists draw this border along the narrowest (western) part of the Torres Strait; according to the definition of the International Hydrographic Bureau, the western boundary of the strait runs from Cape York (11 ° 05 "S, 142 ° 03" E) to the mouth of the Bensbeck River ( New Guinea) (141 ° 01 "E), which also coincides with the eastern border of the Arafura Sea.

The northeastern border of the Indian Ocean runs (from island to island) through the Lesser Sunda Islands to the islands of Java, Sumatra and then to the island of Singapore. On the marginal seas of the Indian Ocean, located along its northern border. The area south of the line between Cape Agulhas and Cape Luin (Western Australia) is sometimes regarded as the southern sector of the Indian Ocean.

Indian Ocean area within the borders excluding the Arafura Sea 74,917 thousand km2, with the Arafura Sea 75,940 thousand km. Average depth 3897 m; the maximum recorded depth is 7437 m3. The volume of water in the Indian Ocean 291,945 thousand km3.

Bottom relief

In bathymetric terms, five morphological units can be distinguished in the Indian Ocean.

Continental margins

The shelves of the Indian Ocean, on average, are slightly narrower than those of the Atlantic Ocean; their width varies from a few hundred meters around some oceanic islands to 200 km or more in the Bombay area. The bend that forms the outer edge of the shelves of Africa, Asia, and Australia has an average depth of 140 m. The boundary of the continental platform is formed by the continental slope, steep marginal ledges, and trench slopes.

The continental slope is cut by numerous underwater canyons. Particularly long submarine canyons lie on the continuation of the mouths of the Ganges and Indus rivers. The continental foot has slopes from 1:40 at the border with the continental slope to 1:1000 at the border with the abyssal plains. The relief of the continental foot is characterized by isolated seamounts, hills and canyons. Submarine canyons at the foot of the continental slope are usually narrow in diameter and difficult to detect, so few of them have been well surveyed. In the areas of the mouths of the Ganges and Indus rivers, large clusters sediments known as archipelagic fans.

The Java Trench stretches along the Indonesian arc from Burma to Australia. From the side of the Indian Ocean, it is bordered by a gentle outer ridge.

ocean bed

The most characteristic elements of the relief of the oceanic bed are the abyssal plains. The slopes here range from 1:1000 to 1:7000. With the exception of isolated tops of buried hills and mid-ocean canyons, the height of the relief of the oceanic bed does not exceed 1–2 m. they are less pronounced. The seaward margins of the abyssal plains are usually characterized by abyssal hills; some areas are characterized by low, linearly elongated ridges.

microcontinents

The most characteristic feature of the topography of the bottom of the Indian Ocean is microcontinents elongated from north to south. In the northern part of the Indian Ocean, in the direction from west to east, the following aseismic microcontinents can be identified: the Mozambique Range, the Madagascar Range, the Mascarene Plateau, the Chagos-Laccadive Plateau, and the Nyntiist Range. In the southern part of the Indian Ocean, the Kerguelen Plateau and the asymmetric Broken Range, elongated from east to west, have a noticeable meridional linearity. Morphologically, the microcontinents are easily distinguished from the mid-ocean ridge; they are usually more high areas arrays with a more leveled relief.

A distinct microcontinent is the island of Madagascar. The presence of granites in the Seychelles also suggests that at least the northern part of the Mascarene Plateau is of continental origin. The Chagos Islands are coral islands, rising above the surface of the Indian Ocean in the area of ​​​​the vast, slightly curved Chagos-Laccadive Plateau. The Nyntiist Ridge is perhaps the longest and straightest ridge discovered in the oceans during the International Indian Ocean Expedition. This ridge was traced from 10°N. sh. up to 32°S

In addition to the microcontinents mentioned above, there is a well-defined Diamantina fault zone in the Indian Ocean 1500 miles west of the southwestern tip of Australia. The Broken Ridge, which forms the northern boundary of this fault zone, at 30°S. sh. connects with the Nyntiist Ridge, which runs at right angles to the Diamantina Fault Zone in a north-south direction.

mid-ocean ridge

The most clearly expressed element of the topography of the bottom of the Indian Ocean is the Central Indian Ridge, part of the global mid-ocean ridge, which in the central part of the Indian Ocean has the shape of an inverted V. A seismically active depression, or rift, stretches along the axis of this mid-ocean ridge. The entire range is generally mountainous with strikes parallel to the axis of the range.

fault zones

The Indian Ocean is dissected by several distinct fault zones that shift the axis of the mid-ocean ridge. East of the Arabian Peninsula and the Gulf of Aden is the Owen Fault Zone, which shifts the axis of the mid-ocean ridge about 200 miles to the right. The recent formation of this offset is indicated by the Whatley Trough, a well-defined depression with depths more than 1000 m greater than the depths of the Indian Abyssal Plain.

Several small right-hand strike slips displace the axis of the Carlsberg Ridge. In the Gulf of Aden, the axis of the mid-ocean ridge is displaced by several left-sided strike-slip faults running almost parallel to the Owen Fault Zone. In the southwestern Indian Ocean, the axis of the mid-ocean ridge is displaced by a series of left-handed fault zones that are roughly in the same orientation as the Owen Fault Zone, The Malagasy Fault Zone, which lies east of the Madagascar Ridge, is likely the southern extension of the fault zone Owen. In the area of ​​the islands of Saint-Paul and Amsterdam, the axis of the mid-ocean ridge is displaced by the Amsterdam fault zone. These zones run parallel to the Nyntiist Ridge and have approximately the same meridional orientation as the fault zones in the western Indian Ocean. Although meridional strikes are most characteristic of the Indian Ocean, the Diamantina and Rodrigues fault zones extend approximately from east to west.

The strongly dissected tectonic relief of the mid-ocean ridge in general presents a noticeable contrast with the very leveled relief of the continental foot and the almost completely smoothed relief of the abyssal plains. In the Indian Ocean, there are regions of smoothly undulating or undulating relief, apparently due to a thick cover of pelagic sediments. The slopes of the mid-ocean ridge south of the polar front are gentler than north of the polar front. This may be a consequence of the higher pelagic sedimentation rate due to the increased organic productivity of the Southern Ocean.

The Crozet Plateau has an exceptionally smooth relief. In this region, the narrow zone of the crest of the mid-ocean ridge usually has a highly dissected relief, while the ocean floor in this region is extremely smoothed.

Climate of the Indian Ocean

Air temperature. In January, the thermal equator for the Indian Ocean is slightly shifted south of the geographic equator, in the region between 10 s. sh. and 20 ju. sh. the air temperature is above 27 ° C. In the northern hemisphere, the 20 ° C isotherm, which separates the tropical from the temperate zone, runs from the south of the Arabian Peninsula and the Gulf of Suez through the Persian Gulf to the northern part of the Bay of Bengal almost parallel to the Tropic of Cancer. In the southern hemisphere, the 10°C isotherm that separates temperate zone from the subpolar, goes almost along the parallel of 45 ° S. In the middle latitudes (southern hemisphere (between 10 and 30°S), the 27–21°C isotherms are directed from WSW to ENE, from South Africa across the Indian Ocean to Western Australia, indicating that the temperature of the western sector at the same latitudes is 1-3°C higher than that of the eastern sector. Off the western coast of Australia, the 27-21°C isotherms descend southward due to the influence of the strongly heated continent.

In May, the highest temperature (above 30°C) is observed in the interior of the southern part of the Arabian Peninsula, Northeast Africa, Burma and India. In India, it reaches more than 35 ° C. The thermal equator for the Indian Ocean lies about 10 ° N. sh. Isotherms from 20 to 10° N lie in the southern hemisphere between 30 and 45° S. sh. from ESE to WNW, indicating that the western sector is warmer than the eastern one. In July, the zone of maximum high temperatures on land shifts north of the Tropic of Cancer.

Temperatures over the Arabian Sea and the Bays of Bengal are slightly lower since May, and in addition, the air temperature in the Arabian Sea is lower than over the Bay of Bengal Near Somalia, the air temperature drops below 25 ° C due to the rise of cold deep waters. The lowest temperatures are observed in August. In the southern hemisphere, the area west of South Africa is somewhat warmer than the central part at the same latitudes. Temperatures are also much higher off the western coast of Australia than in the interior of the mainland.

In November, the thermal equator with a small temperature zone above 27.5 ° C almost coincides with the geographic equator. In addition, over the Indian Ocean region north of 20 ° S. sh. the temperature is almost uniform (25-27 C) except for a small area above central part Indian Ocean.

Annual air temperature amplitudes for the central part, between 10° N. sh. and 12°S w., less than 2.5 C, and for the area between 4 ° C. sh. and 7°S sh. - less than 1 C. In the coastal regions of the Bay of Bengal and the Arabian Sea, as well as in the area between 10 and 40 ° S. sh. west of 100°W e. the annual amplitude exceeds 5 ° С.

Baric field and surface winds. In January, the meteorological equator (minimum Atmosphere pressure 1009-1012 mbar, calm and variable winds), as well as thermal, is located about 10 ° S. sh. it separates the differing meteorological conditions northern and southern hemispheres.

The prevailing wind north of the meteorological equator is the northeast trade wind, or more specifically the northeast monsoon, which changes direction northward at the equator and northwest (northwest monsoon) in the southern hemisphere. To the south of the meteorological equator, due to the heating of the continents in the summer of the southern hemisphere, the minimum pressure (less than 1009 mbar) is observed over Australia, Africa and the island of Madagascar. Region high pressure southern subtropical latitudes is located along 35 ° S.l. the maximum pressure (above 1020 mbar) is observed over the central part of the Indian Ocean (near the islands of Saint-Paul and Amsterdam). The northern bulge of the 1014 mbar isobar in the central Indian Ocean is caused by the effect of more low temperatures air and surface water, in contrast to the South Pacific, where a similar bulge is seen in the eastern sector South America. To the south of the high pressure area, there is a gradual decrease in pressure towards the subpolar depression at about 64.5°S. sh., where the pressure is below 990 mbar. Such a baric system creates two types of wind systems south of the meteorological equator. In the northern part, the southeast trade winds cover the entire Indian Ocean, with the exception of areas near Australia, where they change direction to the south or southwest. South of the trade winds (between 50 and 40°S) there are westerly winds from the Cape of Good Hope to Cape Horn, in an area called the Roaring Forties. The essential difference between the west winds and the trade winds is not only that the former have more high speeds, but also the fact that the daily fluctuations in direction and speed for the former are also much greater than for the latter. In July, for the wind field from the north of 10° S. sh. there is a pattern opposite to January. The equatorial depression with pressure values ​​below 1005 mbar is located above the eastern part of the Asian continent.

South of this depression, the pressure gradually rises from 20 s. sh. to 30°S sh., i.e. to the area of ​​​​the southern borders of the "horse" latitudes. The southern trade winds cross the equator and become in the northern hemisphere the southwest monsoons, very intense, characterized by severe storms off the coast of Somalia in the Arabian Sea.

This area is good example a complete shift of winds with an annual cycle in the northern trade wind zone, which is a consequence of the strong effect of heating and cooling of the Asian continent. In the middle and high latitudes In the southern hemisphere, the moderating effect of the Indian Ocean reduces differences in pressure and wind fields in June and January.

However, at high latitudes, westerly winds increase significantly, and fluctuations in their direction and speed also increase. The frequency distribution of storm winds (more than 7 points) showed that in winter northern hemisphere above for the most part Indian Ocean north of 15°S sh. storm winds are actually not observed (their recurrence is less than 1%). In the region of 10 ° S. latitude, 85–95° E (northwest of Australia) Tropical cyclones occasionally form from November to April, moving southeast and southwest. South of 40°S sh. the frequency of storm winds is more than 10% even in the summer of the southern hemisphere. In the summer of the northern hemisphere, from June to August, the southwest monsoons in the western part of the Arabian Sea (off the coast of Somalia) are always so strong that approximately 10-20% of the winds have a strength of 7 points. During this season, the calm zones (with the frequency of storm winds less than 1%) shift to the area between 1° S. sh. and 7° N. sh. and west of 78° E. e. In the region of 35-40 ° S. sh. the frequency of storm winds increases by 15–20% compared to the winter season.
cloud cover and precipitation. In the northern hemisphere, cloud cover has significant seasonal variations. During the period of the northeast monsoons (December-March), the cloudiness over the Arabian Sea and the Bay of Bengal is less than 2 points. However, in summer the southwest monsoons bring rainy weather to the area of ​​the Malay Archipelago and Burma, while average cloudiness already 6-7 points. The area south of the equator, the zone of southeast monsoons, is characterized by large cloudiness throughout the year - 5-6 points in the summer of the northern hemisphere and 6-7 points in winter. Even in the southeast monsoon zone, there is a relatively large cloud cover and extremely rare patches of cloudless sky, characteristic of the Pacific southeast monsoon zone. Cloudiness in areas west of Australia exceeds 6 points. However, near the coast of Western Australia, it is quite cloudless.

In summer, off the coast of Somalia and the southern part of the Arabian Peninsula, sea fog (20-40%) and very poor visibility are often observed. The water temperature here is 1-2°C lower than the air temperature, which causes condensation, which is intensified by dust brought from the deserts on the continents. Area south of 40°S sh. also characterized by frequent sea fog throughout the year.

The total annual precipitation for the Indian Ocean is high - more than 3000 mm at the equator and more than 1000 mm in the western zone of the southern hemisphere. Between 35 and 20°S sh. in the trade wind zone, precipitation is relatively rare; especially dry is the area off the western coast of Australia - the amount of precipitation is less than 500 mm. The northern boundary of this dry zone is parallel to 12-15°S, i.e., it does not reach the equator, as in the South Pacific Ocean. The northwest monsoon zone is generally the boundary region between the northern and southern wind systems. To the north of this area (between the equator and 10°S) is the equatorial rainy zone, which stretches from the Java Sea to Seychelles. In addition, very a large number of precipitation is observed in the eastern part of the Bay of Bengal, especially in the area of ​​the Malay Archipelago. The western part of the Arabian Sea is very dry, and the amount of precipitation in the Gulf of Aden and the Red Sea is less than 100 mm. The maximum precipitation in rainy zones in December-February is between 10 and 25°S. sh. and in March-April between 5 s. sh. and 10th ju. sh. in the western part of the Indian Ocean The maximum values ​​in the summer of the northern hemisphere are observed in the Bay of Bengal The heaviest rains almost throughout the year are observed to the west of the island of Sumatra.

Temperature, salinity and density of surface waters

February sees typical winter conditions in the northern Indian Ocean. In the interior of the Persian Gulf and the Red Sea, surface water temperatures are 15 and 17.5°C, respectively, while in the Gulf of Aden it reaches 25°C. , the surface waters of the western part of the Indian Ocean are warmer than the surface waters of the eastern part for the same latitudes (the same applies to air temperature).

This difference is caused by water circulation. It is observed in all seasons of the year. In the southern hemisphere, where it is summer at this time, the zone of high temperatures of the surface layer (above 28 ° C) runs in the direction ENE from the eastern coast of Africa to the area west of the island of Sumatra and then south of Java and north of Australia, where the water temperature sometimes exceeds 29°C. Isotherms 25–27°C between 15 and 30S. sh. directed from WSW to ENE, from the coast of Africa to approximately 90-100°E. etc., then they turn to the southwest, as in the western part of the Bay of Bengal, in contrast to the South Pacific, where these isotherms are directed off the coast of South America towards the ENE. Between 40 and 50°S sh. there is a transition zone between water masses of middle latitudes and polar waters, which is characterized by thickening of isotherms; temperature difference of the order of 12 ° C.

In May, the surface waters of the northern Indian Ocean heat up to a maximum and have temperatures mostly above 29 ° C. At this time, the northeast monsoons are replaced by southwest monsoons, although rains and sea level rise are not yet observed at this time. In August, only in the Red Sea and the Persian Gulf does the water temperature reach a maximum (above 30 ° C), however, the surface waters of most of the northern sector of the Indian Ocean, including the Gulf of Aden, the Arabian Sea and most of the Bay of Bengal, with the exception of its western regions, have lower temperatures than in May. The zone of low temperatures of the surface layer (below 25 ° C) stretches from the coast of Somalia to the southeastern coast of the Arabian Peninsula. The decrease in temperature is caused by the intensive rise of cold deep waters due to the southwest monsoons. In addition, in August there are three character traits temperature distributions south of 30°S. latitude: 20–25°C isotherms in the eastern and central parts of the Indian Ocean are directed from WSW to ENE; latitude, and the isotherms to the west of Australia are directed south. In November, the temperature of surface waters is generally close to the average annual temperature. The zone of low temperatures (below 25°C) between the Arabian Peninsula and Somalia and the zone of high temperatures in the western part of the Bay of Bengal are almost disappearing. In a vast area north of 10° S. sh. surface layer temperatures are kept between 27 and 27.7°C.

The salinity of the surface waters of the southern part of the Indian Ocean has the same distributional features that are characteristic of the southern part of the Pacific Ocean. West of Australia there is maximum value salinity (above 36.0 ppm). equatorial zone low salinity, corresponding to the transition zone between the southeast trade winds and monsoons, stretches to 10 ° S. sh., but is clearly expressed only in the eastern part of the Indian Ocean.
The minimum salinity values ​​in this zone are noted south of the islands of Sumatra and Java. The salinity of surface waters in the northern Indian Ocean varies not only regionally but also with the seasons. In the summer of the northern hemisphere, the salinity of surface waters has the following characteristics: it is extremely low in the Bay of Bengal, fairly high in the Arabian Sea, and very high (above 40 ppm) in the Persian Gulf and the Red Sea.

The density of surface waters in the southern part of the Indian Ocean in the summer of the southern hemisphere decreases uniformly in a northerly direction from about 27.0 in the region of 53-54 ° S. sh. to 23.0 at 17°S sh.; in this case, the isopycnals run almost parallel to the isotherms. Between 20°S sh. and 0° there is a huge zone of low-density waters (below 23.0); near the islands of Sumatra and Java, there is a zone with a density below 21.5, corresponding to the zone of minimum salinity in this area. In the northern part of the Indian Ocean, salinity affects the change in density. In summer, the density decreases from 22.0 in the southern part of the Bay of Bengal to 19.0 in its northwestern part, while for most of the Arabian Sea it is above 24.0, and near the Suez Canal and in the Persian Gulf it reaches 28.0 and 25.0. In addition, seasonal changes in surface water density are mainly driven by temperature changes. Thus, for example, the northern part of the Indian Ocean is characterized by an increase in density by 1.0–2.0 from summer to winter.

Currents of the Indian Ocean

Currents in the northern Indian Ocean, which are under strong influence monsoons and seasonally varying are called the southwest and northeast monsoon drifts for summer and winter, respectively. The Southern Equatorial Current and the West Wind Current pass through the southern part of the Indian Ocean. In addition to these currents, closely related to wind systems, there are currents of a local nature, caused mainly by the density structure of the Indian Ocean, such as the Mozambique Current, the Cape of Needle Current, the Intertrade (Equatorial) Countercurrent, the Somali Current and the West Australian Current.

In the southern part of the Indian Ocean, there is a large anticyclonic circulation, similar to the circulation in the southern parts of the Pacific and Atlantic oceans, but here this circulation is subject to more significant annual changes. Its extreme southern part is the current of the West Winds (between 38 and 50 ° S. latitude), 200-240 miles wide, intensifying in an easterly direction. This current borders on the subtropical and antarctic convergence zones. The speed of the current depends on the strength of the wind and varies seasonally and regionally. Max Speed(20-30 miles/day) observed near Kerguelen Island. In the summer of the southern hemisphere, this current turns north when approaching Australia and joins with the current coming from the Pacific Ocean south of Australia.

In winter, the wind drift joins with the current flowing south along the western coasts of Australia and continues into the Pacific Ocean along southern shores Australia. The eastern part of the anticyclonic circulation in the southern hemisphere is the West Australian Current, which has a steady northerly direction only in the summer of the southern hemisphere and reaches 10–15 miles/day north of 30°S. sh. This current becomes weak in winter and changes direction to the south.

The northern part of the anticyclonic circulation is the South Trade Wind Current, which originates in the region where the West Australian Current exits to the Tropic of Capricorn under the influence of the southeast trade winds. The maximum current speed (more than 1 knot) is observed in its eastern part in the winter of the southern hemisphere, when the western flow from the Pacific Ocean intensifies north of Australia. In the summer of the southern hemisphere, when this current becomes easterly, the northern boundary of the South Equatorial Current is between 100 and 80°E. d. is located about 9 ° S. sh., slightly shifting southeast of 80 ° E. d.; its southern border passes at this time about 22 ° S. sh. in the eastern sector. In the winter of the southern hemisphere, the northern boundary of this current shifts northward by 5-6°, following the northward shift of the southeast trade wind. Before the island of Madagascar, the current is divided into several branches.

One of them goes north around the island of Madagascar at a speed of up to 50-60 miles / day and then turns west. It again divides into two branches at Cape Delgado. One branch turns north (East African Coastal Current), the other turns south through the Mozambique Channel (Mozambique Current). The speed of this current varies from almost zero to 3-4 knots during the northeast monsoon.

The current of Cape Agulhas is formed from the continuation of the Mozambique Current and the southern branch of the South Trade Wind Current south of the island of Mauritius. This current, narrow and clearly defined, extends from the coast for less than 100 km. As is known, a southward flow in the Southern Hemisphere is characterized by a tilt of the water surface to the left. At a distance of 110 km from Port Elizabeth, the tilt towards the ocean increases by approximately 29 cm. Between Durban and 25 ° E. e. the speed of this current near the edge of the Agulhas Bank reaches 3-4.5 knots. South of Africa, the main body of the current turns sharply to the south and then to the east and unites, thus with the course of the West Winds. However, it is small and at the same time continues to move into the Atlantic Ocean. Due to the change of direction and the forked current, numerous eddies and eddies develop along the coast of South Africa, the position of which changes during the year.

North of 10°S sh. There is a strong variability in the surface currents of the Indian Ocean from winter to summer. During the period of the northeast monsoon, from November to March, the North Trade Wind (drift of the northeast monsoon) develops. The southern boundary of this current varies from 3–4°N. sh. in November to 2-3°S. sh. in February. In March, the current turns north again and disappears with the advent of the drift of the southwest monsoon. With the advent of the northeast monsoon (since November), the trade wind countercurrent begins to develop. It is formed under the combined influence of the current running southwest of the coast of Somalia and the East African coastal current going north from the cape. Delgad. The countercurrent is narrow and reaches almost to the island of Sumatra. Its northern boundary in November passes north of the equator, and in February it shifts to 2-3°S. Later, the current rises again to the north and then disappears. The southern boundary of the current lies between 7 and 8°S. sh. Current velocity between 60 and 70°E. reaches 40 miles / day, but further to the east it decreases.

During the period of the southwest monsoon, from April to October, the North Trade Wind (the drift of the northeast monsoon disappears and is replaced by the drift of the southwest monsoon, going east south of India. South of the island of Sri Lanka, its speed is 1-2 knots, and sometimes reaches 3 knots The branches of this current create a clockwise circulation in the Arabian Sea, following the contours of the coastline.The speed of the southeast current off the western coast of India reaches 10-42 miles / day.During this season, the Somali current along the coast of Somalia in the region of 10 ° S is directed north, and the waters of the South Equatorial Current cross the equator Off the coast of Somalia, an intensive rise of waters occurs, causing cooling of surface waters over a large area.

Subsurface currents in the Indian Ocean north of 10°S sh. were measured at the horizons of 15, 50, 100, 200, 300, 500 and 700 m during the 31st voyage of the Vityaz (January-April 1960), at about 140 deep-sea stations.

It has been established that at a depth of 15 m, the distribution of currents turned out to be almost similar to that in the surface winter of the northern hemisphere, except that, according to observations, the Equatorial countercurrent originates at 60°E. and captures the area between 0 and 3 ° S.l. those. its width is much less than on the surface. On the horizon, 200 m of current south of 5 ° N. sh. have direction reverse currents on the horizon of 15 m: they are directed east under the North and South Equatorial currents and west under the Intertrade countercurrent east of 70 ° E. e. At a depth of 500 m of current between 5 ° N. sh. and 10°S sh. generally have an easterly direction and form a small cyclonic gyre centered at 5°S. latitude, 60° east In addition, direct measurements of the currents and data from dynamic calculations for the period November-December 1960, obtained during the 33rd voyage of the Vityaz, indicate that the observed system of currents does not yet correspond to the system of currents characteristic of the winter monsoon , despite the fact that northwest winds are already beginning to prevail here. At a depth of 1500 m south of 18° S. sh. an eastward current was detected at a speed of 2.5–45 cm/s. About 80° E. e. this current is combined with the southern stream, which has a speed of 4.5-5.5 cm / s and its speed increases rapidly. About 95° E. This current turns sharply to the north and then to the west, forming an anticyclonic gyre, the northern and southern parts of which have velocities of 15-18 and 54 cm/s, respectively.

About 20-25°S latitude, 70–80° E e. the southward branch of this current has a velocity of less than 3.5 cm/s. On the 2000 m horizon between 15 and 23° S. sh. the same current has an easterly direction and a speed of less than 4 cm/s. About 68° E. e. a branch departs from it, going north at a speed of 5 cm / s. Anticyclonic gyre between 80 and 100°E. on the horizon 1500 m covers large area between 70 and 100° E. e. A current going south from the Bay of Bengal meets another current coming from the east at the equator and turns north and then northwest to the Red Sea.

On the 3000 m horizon between 20 and 23° S. sh. the current is directed to the east with velocities in some places up to 9 cm/s. Cyclonic circulation at 25-35° S. latitude, 58—75° E becomes clearly expressed here at speeds up to 5 cm / s. Anticycloic circulation between 80 and 100 c. observed at a horizon of 1500 m, breaks up here into a series of small eddies.

water masses

For the Indian Ocean, in addition to the subantarctic water mass, three main water masses are characteristic: the central water mass of the Indian Ocean (subtropical subsurface), the equatorial water mass of the Indian Ocean, extending to medium depths, and the deep water of the Indian Ocean, below the horizon of 1000 m. There are also intermediate water masses. These are the Antarctic intermediate waters, the waters of the Red Sea, and others at medium depths.

Located in the northern Indian Ocean. In the east it is bounded by the Indochina peninsula, in the west by the Andaman Islands, in the south by the island of Sumatra. Sea area - 605 thousand sq. km, average depth- 1043 m, the highest reaches 4507 m.

Like many tropical waters, the Andaman Sea boasts a rich underwater world. More than 400 species of fish live here, among which there are such unusual ones as sailboats and flying fish, angel fish and butterfly fish.

Currently, the Andaman Sea is one of the most popular tourist centers. Its coast is a whole constellation of world-famous resorts - Phuket, Krabi, Phi Phi Islands, Kuala Lumpur.

Located in the northern part of the ocean between two large peninsulas Asia: Arabian and Hindustan. The area of ​​the sea is 3.8 million sq. km, the average depth is 2734 m, the maximum depth is 4652 m.

The sea is named after the peninsula of the same name, but in ancient times it was called quite differently: Green, Omani, Eritrean, Persian, Sindhu Sea.

By the number of inhabitants of the underwater world, the Arabian Sea is one of the richest on earth. Only commercial species Over 100 fish live here.

The sea has a lot transport value. First, here are the main sea ​​routes going through the Suez Canal. Secondly, by Arabian Sea oil is transported from the Persian Gulf.

Separates Australia from the island of New Guinea. The area is 1 million sq. km, the average depth is 186 m, although the greatest depth is recorded at around 3680 m.

The sea got its name from the name of the local tribe, the natives of the Moluccas - "alfurs". Translated from the local dialect, "alfura" means "inhabitant of the forests."

One of the richest seas The Indian Ocean, which is home to almost a third of all species of flora and fauna represented in this ocean.

One of the attractive features of the Arafura Sea is its clean and clear water. The lands surrounding the reservoir are sparsely populated. There is no mining activity and no major ports. Therefore, nothing threatens the ecology of the sea yet.

A long ribbon stretched along the coast of Egypt, Sudan, Saudi Arabia, Israel, Djibouti, Jordan and Yemen. It is an inland sea separating Africa and Asia. The area is 450 thousand sq. km, the average depth is 437 m.

The Red Sea is considered the most salty in the world. 1 liter of water here contains 41 g of salt (for comparison: in the Black - 18 g, in the Baltic - 5 g). There are two reasons for this salinity:

1. Not a single river flows into the Red Sea. But it is the rivers that desalinate the sea water.

2. A lot of metal-bearing brines were found at the bottom of the sea.

The uniqueness of the Red Sea and that it is the richest in species diversity among all bodies of water in the northern hemisphere. There are 13 species of sharks, 14 species of moray eels, and among hundreds of species of fish, 30% are endemic.

The Red Sea is also the most transparent in the world. It is no coincidence that divers love it so much and often call it an "underwater resort".

marginal sea located between southwest coast Hindustan, Laccadive Islands and Maldives. The area is 786 thousand sq. km, the average depth is 1929 m.

In spite of monsoon climate, sea all year round remains warm, in summer the water temperature is 28-29ºC, in summer it rarely drops below +25ºC. The southern part of the sea abounds with corals. This sea is the main industrial maritime region for India, where fishing and shrimp and lobster fishing flourish.

Separates Australia and the island of Timor. The area is 432 thousand sq. km, the average depth is 435 m.

The Timor Sea is famous for its hydrocarbon reserves. Oil and gas production has already been established here and new deposits are being searched. Proximity to the equator determined the climate - the waters of the water area are warm throughout the year, storms - a rare thing. But shallow water has become the reason that typhoons often dominate here, especially during the rainy season.

Translated from Portuguese, "Timorese" means "orange sea".

Many seas wash the shores of one or more countries. Some of these seas are huge, others are very small... Only the inland seas are not part of the ocean.

After the Earth formed from a bunch of gas and dust 4.5 billion years ago, the temperature on the planet dropped and the vapor contained in the atmosphere condensed (turned into liquid when cooled), settling on the surface in the form of rain. From this water, the world ocean was formed, subsequently divided by the continents into four oceans. These oceans include numerous coastal seas, often interconnected.

The largest seas of the Pacific Ocean

Philippine Sea
Area: 5.7 million km2, located between Taiwan in the north, the Marianne Islands in the east, the Caroline Islands in the southeast and the Philippines in the west.

coral sea
Area: 4 million km 2, bounded in the west by Australia, Papua New Guinea in the north, Vanuatu in the east and New Caledonia

South China Sea
Area: 3.5 million km 2, located between the Philippines in the east, Malaysia in the south, Vietnam in the west and China in the north

tasman sea
Area: 3.3 million km 2, washes Australia in the west and New Zealand in the east and separates the Pacific and Indian oceans.

Bering Sea
Area: 2.3 million km 2, located between Chukotka (Russia) in the west and Alaska (USA) in the east.

Japanese Sea
Area: 970,000 km2, located between the Russian Far East in the northwest, Korea in the west and Japan in the east.

Major seas of the Atlantic Ocean

Sargasso Sea
Area: 4 million km 2, located between Florida (USA) in the west and the northern Antilles in the south.

Composition of sea water

Sea water is approximately 96% water and 4% salt. Apart from the Dead Sea, the most salty sea in the world is the Red Sea: it contains 44 grams of salt per liter of water (against 35 grams on average for most seas). Such a high salt content is due to the fact that in this hot region, water evaporates faster.

gulf of guinea
Area: 1.5 million km 2, located at the latitude of the Ivory Coast, Ghana, Togo, Benin, Nigeria, Cameroon, Equatorial Guinea and Gabon.

Mediterranean Sea
Area: 2.5 million km 2, surrounded by Europe in the north, Western Asia in the east and North Africa on South.

Antilles Sea
Area: 2.5 million km 2, located between the Antilles in the east, the coast of South America in the South and Central America in the West.

Gulf of Mexico
Area: 1.5 million km 2, it is adjacent to the southern coast of the United States from the north and Mexico from the west.

Baltic Sea
Area: 372,730 km 2 , washes Russia and Finland in the north, Estonia, Latvia and Lithuania in the east, Poland and Germany in the south and Denmark with Sweden in the west.

North Sea
Area: 570,000 km2, bordered by Scandinavia to the east, Germany, the Netherlands, Belgium and France to the south, and Great Britain to the west.

Major seas of the Indian Ocean

Arabian Sea
Area: 3.5 million km 2, washes the Arabian Peninsula in the west, Pakistan in the north and India in the east.

bay of bengal
Area: 2.1 million km 2, located between the coasts of India in the west, Bangladesh in the north, Myanmar (Burma) in the northeast, the Andaman and Nicobar Islands in the southeast and Sri Lanka in the southwest.

Great Australian Bight (Australian Bight)
Area: 1.3 million km 2, extends along south coast Australia.

Arafura Sea
Area: 1 million km 2, located between Papua New Guinea in the northwest, Indonesia in the west and Australia in the south.

mozambique channel
Area: 1.4 million km 2, located near Africa, between the coasts of Mozambique in the west and Madagascar in the east.

The largest seas of the Arctic Ocean

Barents Sea
Area: 1.4 million km 2, washes the coast of Norway in the west and Russia in the east.

Greenland Sea
Area: 1.2 million km 2, bounded by Greenland in the west and the island of Svalbard (Norway) in the east.

East-Siberian Sea
Area: 900,000 km 2, washes the coast of Siberia.

The largest seas of Antarctica

inland seas

Inland, or closed, seas are completely surrounded by land. Black and Caspian Sea- the largest of them.

Black Sea
Area: 461,000 km2. It is surrounded by Romania and Bulgaria to the west, Russia and Ukraine to the north, Georgia to the east and Turkey to the south. It communicates with mediterranean sea through Marble.

Bellingshausen Sea
Area: 1.2 million km 2, located near Antarctica.

Caspian Sea
Area: 376,000 km2, located between Azerbaijan in the west, Russia in the northwest, Kazakhstan in the north and east, Turkmenistan in the southeast and Iran in the south.

Ross Sea
Area: 960,000 km2, located north of Antarctica.

Weddell Sea
Area: 1.9 million km 2, located between the South Orkney Islands (UK) and the South Shetland Islands (UK) in the north and Antarctica in the south.

The Dead Sea is so salty that there are no living organisms in it.

The Indian Ocean is 20% of the world's oceans by volume. It is bounded by Asia to the north, Africa to the west, and Australia to the east.

In the zone of 35 ° S passes the conditional border with the Southern Ocean.

Description and characteristics

The waters of the Indian Ocean are famous for their transparency and azure color. The fact is that few freshwater rivers, these "troublemakers," flow into this ocean. Therefore, by the way, the water here is much saltier than in others. The Red Sea, the saltiest sea in the world, is located in the Indian Ocean.

And the ocean is rich in minerals. The region near Sri Lanka has been famous for its pearls, diamonds and emeralds since ancient times. And the Persian Gulf is rich in oil and gas.
Area: 76.170 thousand sq. km

Volume: 282.650 thousand cubic km

Average depth: 3711 m, the greatest depth is the Sunda Trench (7729 m).

average temperature: 17°C, but in the north the waters warm up to 28°C.

Currents: two cycles are conditionally distinguished - northern and southern. Both move clockwise and are separated by the Equatorial Countercurrent.

Major currents of the Indian Ocean

Warm:

Northern Tradewind- originates in Oceania, crosses the ocean from east to west. Beyond the peninsula, Hindustan is divided into two branches. Part flows to the north and gives rise to the Somali current. And the second part of the flow goes south, where it merges with the equatorial countercurrent.

South Passatnoe- begins at the islands of Oceania and moves from east to west up to the island of Madagascar.

Madagascar- branches off from the South Tradewind and flows parallel to the Mozambique from north to south, but slightly east of the Madagascar coast. Average temperature: 26°C.

mozambican is another branch of the South Tradewind Current. It washes the coast of Africa and merges with the Agulhas in the south. The average temperature is 25°C, the speed is 2.8 km/h.

Agulhas, or the course of Cape Agulhas- narrow and rapid current running along the east coast of Africa from north to south.

Cold:

Somali- a current off the coast of the Somali peninsula, which changes its direction depending on the monsoon season.

The course of the West winds encircles Earth in southern latitudes. In the Indian Ocean, from it is the South Indian Ocean, which, near the coast of Australia, passes into the West Australian.

Western Australian- moves from south to north along the western coast of Australia. As you get closer to the equator, the water temperature rises from 15°C to 26°C. Speed: 0.9-0.7 km/h.

Underwater world of the Indian Ocean

Most of the ocean is located in the subtropical and tropical zones, and therefore rich and diverse in terms of species.

The coast of the tropics is represented by vast thickets of mangroves, home to numerous colonies of crabs and amazing fish- mud jumpers. Shallow waters are a great habitat for corals. And in temperate waters, brown, calcareous and red algae (kelp, macrocysts, fucuses) grow.

Invertebrates: numerous mollusks, a huge number of species of crustaceans, jellyfish. Many sea ​​snakes, especially poisonous ones.

Sharks of the Indian Ocean are a special pride of the water area. The largest number of shark species live here: blue, gray, tiger, great white, mako, etc.

Of the mammals, dolphins and killer whales are the most common. BUT South part ocean is natural environment habitats of many species of whales and pinnipeds: dugongs, seals, seals. Most of the birds are penguins and albatrosses.

Despite the richness of the Indian Ocean, the seafood industry is poorly developed here. The catch is only 5% of the world. They harvest tuna, sardines, rays, lobsters, lobsters and shrimp.

Indian Ocean exploration

Coastal countries of the Indian Ocean - pockets ancient civilizations. That is why the development of the water area began much earlier than, for example, the Atlantic or the Pacific Ocean. Approximately 6 thousand years BC. the waters of the ocean were already plowed by shuttles and boats of ancient people. The inhabitants of Mesopotamia sailed to the shores of India and Arabia, the Egyptians carried on a brisk maritime trade with the countries East Africa and the Arabian Peninsula.

Key dates in the history of ocean exploration:

7th century AD - Arab sailors draw up detailed navigational charts of the coastal zones of the Indian Ocean, explore the water area near the eastern coast of Africa, India, the islands of Java, Ceylon, Timor, and the Maldives.

1405-1433 - seven sea ​​voyages Zheng He and the study of trade routes in the northern and eastern parts of the ocean.

1497 - Vasco de Gama sails and explores the east coast of Africa.

(Expedition of Vasco de Gama in 1497)

1642 - two raids by A. Tasman, exploration of the central part of the ocean and the discovery of Australia.

1872-1876 - the first scientific expedition of the English corvette "Challenger", the study of the biology of the ocean, relief, currents.

1886-1889 - expedition of Russian explorers led by S. Makarov.

1960-1965 - International Indian Ocean Expedition, established under the auspices of UNESCO. The study of hydrology, hydrochemistry, geology and biology of the ocean.

1990s - present: studying the ocean with the help of satellites, compiling a detailed bathymetric atlas.

2014 - after the crash of the Malaysian Boeing, detailed mapping of the southern part of the ocean was carried out, new underwater ridges and volcanoes were discovered.

The ancient name of the ocean is Eastern.

Many species of wildlife in the Indian Ocean have an unusual property - they glow. In particular, this explains the appearance of luminous circles in the ocean.

In the Indian Ocean, ships are periodically found in good condition, however, where the entire crew disappears remains a mystery. Over the past century, this has happened to three ships at once: the ship "Cabin Cruiser", the tankers "Houston Market" and "Tarbon".

Less extensive than Quiet and. Its area is 76 million km2. This ocean is widest in the Southern Hemisphere, and in the Northern Hemisphere it looks like a large sea, deeply cutting into the land. Exactly major sea the Indian Ocean was presented to people from ancient times up to.

The shores of the Indian Ocean are one of the areas of ancient civilizations. Scientists believe that navigation in it began earlier than in other oceans, about 6 thousand years ago. The Arabs were the first to describe ocean routes. The accumulation of information about the Indian Ocean began from the time of the voyage (1497-1499). At the end of the 18th century, the first measurements of its depths were made by an English navigator. The comprehensive study of the ocean began in late XIX century. Most major studies were carried out by an English expedition on board the Challenger. Nowadays, dozens of expeditions from different countries are studying the nature of the ocean, revealing its riches.

The average depth of the ocean is about 3700 meters, and the maximum reaches 7729 meters in the Yavan Trench. An underwater ridge stretches in the western part of the ocean, connecting to the south with the Mid-Atlantic Ridge. Deep faults, areas and at the bottom of the ocean are confined to the center of the ridge in the Indian Ocean. These faults continue into and out on land. The ocean floor is crossed by numerous uplifts.

Location: The Indian Ocean is bounded from the north by Eurasia, from the west by the east coast of Africa, from the east by the western coast of Oceania, and from the south by the waters South Sea, the border of the Atlantic and Indian Oceans runs along the 20th meridian of E. D., between the Indian and Pacific Oceans - along the 147th meridian of E. d.

Area: 74.7 million km2

Average depth: 3 967 m.

Maximum depth: 7729 m (Zonda, or Yavansky, trench).

: from 30‰ to 37‰.

Additional Information: in the Indian Ocean there are islands, Sri Lanka, Socotra, Laccadive, Maldives, Andaman and Nicobar, Comoros, and some others.